The value of weight-bearing exercise

Gunnar Mossberg

Studies have shown that most bone is formed in adolescence. According to Dr. Karim Khan, a professor at the University of British Columbia, the peak age for bone growth in females is 12.5 years, and in males it is 14 years.

Females gain 40 percent to 50 percent of their skeletal mass during adolescence. It has been shown clearly that exercise results in increased bone density and strength. If started during adolescence and young adulthood, the bone mineral density at the lumbar spine and femoral neck (hip) has been shown to be significantly greater at age 28 in males and females than if no such exercise had been performed during this age. A recent Swedish study on former soccer players showed that these athletes had higher bone density at the leg for up to 25 years after they stopped competing.

It has been reported that 30 percent of women 70 or older fall regularly, with 20 percent of resulting fractures leading to death. Khan showed that people who performed regular, moderate to intense training to increase strength had a 50 percent reduction in fall risk.

Other research has shown that elderly women who walked four hours per week lowered their relative risk of hip fractures by 41 percent. Yet another study out of Yale University showed that physically frail older adults in their 80s who performed resistive exercise, balance exercise and conditioning exercise three times per week for six months, initially supervised by a physical therapist, had a 37 percent reduction in risk of new disability and they had “significantly fewer falls” than people not exercising.

We know that weight-bearing exercise builds more bone mass than non-weight-bearing exercise. It has been shown that in children and perimenopausal women, jumping strengthens the bone the most, and adults who perform high-intensity strengthening exercise achieve the highest increase in bone mineral density. However, people who have known joint arthritis or painful musculoskeletal conditions may need a modified exercise program, and should always first be seen by a physical therapist or physician.

Khan’s studies demonstrated that calcium intake in adolescence produces only a temporary increase in bone density, whereas exercise leads to long-lasting bone strength. However, he also showed that calcium supplementation combined with vitamin D was important later in life.

The sooner we start exercise the more we build up bone for later in life. Exercise for the elderly can have a lifesaving effect.